2.9 misfires while alternator is working.

[dirtracer11591]

Long shot
Try grounding alternator to battery negative, if you have jumper cables use it from alternator adjuster bolt to battery negative terminal
See if that allows engine to run smoother


No, ammeter working or not shouldn't effect anything, but would be good to have it working

Unfortunately I already tried to directly ground the alternator case to no avail.

Im convinced I've got some kind of wild coincidence going on here. I've just got to figure out how the alternator which I've verified is functioning as intended is having such a drastic effect on the ignition system.

 

[Bear in the woods]

Sure is not the throttle position sensor. If you ignore the whole battery issue.i believe That is the symptoms of a bad one. But I haven’t been a mechanic in a long time

 

[Bear in the woods]

All of these wires check out. The only thing I seen off is his Ammeter doesn't seem to be moving. Sits just off center toward the C and doesn't seem to move with engine on or off. But I've tested the voltage at the battery and confirmed the alternator is charging. Would a malfunction in the Ammeter effect the function of the alternator?

Try grounding the ammeter wire. The gauge should move if it’s functioning

 

[dirtracer11591]

Sure is not the throttle position sensor. If you ignore the whole battery issue.i believe That is the symptoms of a bad one. But I haven’t been a mechanic in a long time

Early on i did unplug the TPS to see if it would force it into a "limp mode" on the alpha-n map but it made no difference. I didnt actually touch my meter to it. I guess going back and verifying the function of all the parts the previous mechanics threw at it like the TPS would be my best course of action now.

 

[franklin2]

Try grounding the ammeter wire. The gauge should move if it’s functioning

I would not do that. Ever heard of "letting the smoke out"? Both factory ammeter wires are hot wires.

 

[dirtracer11591]

I wanted to update this thread that the problem was SOLVED. Back tracking through parts that had already been replaced multiple times by the mechanics before me I found the new TFI had some substantially higher resistances than it should. Replaced it with a TFI that had already been on the truck with the correct resistances while other people were trying to fix it and the misfire cleared right up. I imagine the high resistance in the TFI was causing the ignition to cut out under load, now why the alternator being unplugged cleared up the issue I am not entirely sure. I did fix a couple other small things while I was in there and ultimately it could have just been a combination of things stumping the guys who worked on it before me. Regardless my buddy said it is running the best it has since he bought it.

 

[Bill4]

Life saver. Thank you. Last time my distributor took a dump on my 93 3.0 I replaced the tfi with an autozone one. A few weeks later my truck started misfiring under high electric load. Unhook the alt it ran fine. It cost me a new battery and alternator before I saw your post. But it finally runs

 

[Spazzzola]

I’m having this same issue with my 2.3 Lima. Can you lead me to some of the things you may have fixed with the other mechanic solutions? I even went and got a new tfi and that did not help. In fact for me I thought the tfi was my issue then I found the alternator anomaly.

 

[Bill4]

I had ran new grounds to the block, body and frame. Replaced the charge wire from alternator. Checked fuel pressure. Replaced the alternator 3 times with used ones I had laying around. The next test I was going to try was to unhook the alternator and put the big car charger on it to see if it still did it with a different charge source.
Im pretty sure my tfi was bad right from new
I'm going to buy another original one from a junk yard to have in glove box.

 

[Chad302]

Has anyone found the actual problem to this? Mine does the same thing, put the top plug for the alternator and truck runs great plug it in and runs like crap

 

[franklin2]

Has anyone found the actual problem to this? Mine does the same thing, put the top plug for the alternator and truck runs great plug it in and runs like crap

He said he replaced the TFI and it fixed it in a previous post in this thread.

 

[Chad302]

I’ve replaced everything and still have the problem

 

[Mark clapper]

I’ve replaced everything and still have the problem
[/QUOTE same here I’ve put 2 different to modules in and it’s still the same

 

[Wilcox]

I have some problem? Did you ever figure out what was causing it to miss fire. I'm pulling my hair out on this.

 

[Jazzer]

Wilcox, if you read back in this thread you’ll see he had a bad TFI. Hope that fixes yours.